The present invention relates to an apparatus and method for injecting ozone into a pressurized water stream in a water main wherein water pressure in the main varies with respect to time. The apparatus and method separate a portion of the main water stream into a side stream and direct the side stream through a loop having a plurality of vertically spaced crossovers. Flow is directed through a particular crossover that is selected in accordance with the pressure of the water. Ozone is injected under reduced pressure into the top of the loop.
In many locations fresh water supplies are stored in reservoirs that may be natural lakes or formed behind dams along rivers and the like. Such water is transferred, often utilizing hydraulic forces created by the depth of the water in a reservoir, under pressure through piping to users in a city or the like. Normally, such water is treated in some manner to disinfect the water. A common disinfecting technique is to inject ozone into the water to kill microorganisms in the water.
While modern technology makes it relatively easy to produce ozone from either pure oxygen or from air, there are problems associated with use of such ozone in water systems that are derived from reservoirs of the type noted above. In particular, the ozone must somehow be injected into the water stream in order for it to disinfect the water. Water is normally drawn off of a reservoir from a comparatively low region of the reservoir so that the reservoir may be essentially drained, if need be. Because of this, there is normally a fairly substantial hydraulic pressure associated with the water, since the normal level in a reservoir is kept substantially above the empty level.
There may be several hundred feet or more of water above the location where the water is withdrawn from the reservoir. While this hydraulic pressure may be effectively used to transport the water to the city where the water is used, it creates a substantial back pressure which must be overcome, if ozone is to be injected into the water. To inject ozone at high pressures, comparatively large oxygen/ozone gas compressors are required that must be constructed of suitable materials that are able to withstand contact with ozone on a continuous basis. When such compressors are required to produce relatively high pressures, they are comparatively very expensive to construct, operate and maintain. Such compressors are also comparatively very noisy.
While high pressure oxygen/ozone compressors are very expensive and limited in availability, oxygen supply and ozone generator equipment systems are readily available with the capability to produce ozone at a pressure of at least fifteen pounds per square inch gauge (psig) for injection directly into a relatively low pressure water system without the use of large oxygen/ozone gas compressors. The readily available low pressure systems must still be constructed to withstand ozone, but are in comparison substantially less expensive to construct and operate and substantially less noisy than systems using oxygen/ozone gas compressors that are designed to inject the same amount of ozone into water with a much higher back pressure.
Therefore, it became important with respect to the present invention to construct equipment and design methods which allow injection of ozone into water at a comparatively low pressure even though the source of the water has a relatively high hydraulic pressure. It is also important with respect to the present invention that the overall cost of the equipment necessary to allow injection of ozone at a lower pressure not be so costly as to offset the short term and long term savings produced by injecting the ozone at a comparatively lower pressure.